Tap hole mix



TAP HQLE MEX Leroy C. Werlring, (Ileveland, Ohio, assignor to UnionCarbide and Qarbon Corporation, a corporation of New York No Drawing.Application June 30, 1951, Serial No. 234,655

@laims. (Cl. Tile-56) This invention relates to tap hole mixes to beused for closing (plugging) the tap holes of blast furnaces and thelike.

For the removal of molten metal from blast furnaces and the like a taphole must be provided. This tap hole extends through the lining of thefurnace into the hearth and communicates with a trough on the outside ofthe furnace for directing tapped, molten metal to a ladle or otherreceptacle. Between casts from the furnace the tap hole must of coursebe closed, and for closing it, it is conventional practice to extrude amass of water wet clay from a mud gun into the hole. With such clay maybe admixed crushed fire brick, coke or coal and the like to make the mixmore porous. Such ceramic or carbonaceous materials may, of course, bepresent in the mix of the invention, and are referred to in the appendedclaims as fillers. The heat of the furnace causes the clay to set up,forming a refractory plug in the tap hole. When the time comes to tapthe furnace this plug is partially drilled out, and conventionally isthen subjected to the action of an oxygen lance to burn through into thefurnace hearth or until the molten metal starts to flow from thefurnace.

For many years carbon has been recommended as a lining material forblast furnaces, particularly in the hearth, and because of its excellentcharacteristics, its use for this purpose has become rather widespread.More recently, carbon has been used as a lining in the immediatevicinity of the tap hole as well as in other portions of the furnace,but here some difliculty has been encountered in that there is a loss ofcarbon in the vicinity of the tap hole during use of the furnace. Thisloss of carbon manifests itself by a gradual thinning of the lining andthe formation of a funnel-shaped depression in the zone surrounding thetap hole. If unchecked, such carbon loss would lead to a runout, thatis, accidental discharge of molten metal from the furnace.

it is the principal object of this invention to prevent this destructionof the carbon lining. More specifically, it is an object of theinvention to provide a novel tap hole mix for plugging the tap holes ofblast furnaces and the like.

The invention by means of which this object is attained is based on thediscovery that the destruction of carbon in the vicinity of the tap holeis attributable in part to reaction between steam evolved from the wetclay used to plug the tap hole and the carbon and in part to reaction ofoxygen from the oxygen lance with the carbon. Such reactions areexemplified by the following equations:

(2) CO2+C=2CO (3) C+O2=CO2 In accordance with the present inventionReactions 1 and 2 are substantially prevented from taking place byutilizing a tap hole mix which is substantially free of 2,709,659Patented May 31, 1955 ice water, and the detrimental effect of Reaction3 is substantially avoided by the deposition of carbon from the noveltap hole mix used.

The invention comprises a tap hole mix consisting of at least onecomminuted solid such as milled clay, crushed fire brick, coke or coal,clay being preferred, and a carbonaceous thermosetting, carbonizablebinder. The binder is composed of resin-forming organic material such asa phenol-aldehyde composition or a mixture of tar and aldehyde such asfurfural so compounded as to be thermosetting. Preferably the binder isa material which will remain plastic at room temperature for anindefinite time but which hardens quickly at temperatures of about 400F. Such a mixture is extrudable from a conventional mud gun, hardensalmost instantaneously in the zone of a tap hole close to the furnacehearth and less quickly in the zone farther removed from the furnacehearth. An essential characteristic of the mix of the invention issubstantial freedom from water, and another essential property is thatit be thermosetting.

In the tap hole mix of the invention the proportion of a solid to bindershould be about 3 to 1 to 5 to 1, varying between these extremes to suitthe desires of the operator. Typically, a tap hole mix according to theinvention may contain by weight about solids, preferably milled clay,and 20% binder, although as in conventional practice, the clay may beadmixed with crushed fire brick, coke or coal as filler materials. Asabove indicated such binder may be an anhydrous heathardenable A stagephenol-aldehyde reaction product. Such binder may include a conventionalacid or alkaline catalyst. A preferred tap hole mix is composed ofmilled clay and a binder consisting of tar, furfural and an acceleratorsuch as sulfur. Typically such a composition contains 80% to 82% ofcomminuted solid material, 11% to 12% tar, 5% to 6% furfural and 1% to2% sulfur. A specific example of this type of mix contains by weight,81% milled clay, 11.7% tar, 5.8% furfural and 1.5% sulfur. This mix willremain completely plastic at room temperature for several weeks but willbecome hard and infusible in two hours at 400 F. At the temperatureexisting in the hot zones of a tap hole it will set almostinstantaneously.

Tests of the tap hole mix of the invention have been made on full-sizeiron blast furnaces using a mix of the specific composition just given.The mix was prepared during the course of these tests by mixing milledclay with the binder, the binder having been previously prepared. Themix was readily extruded from the mud gun and was successfully used toplug the tap hole, hardening quickly in place. in one series of teststhe tap hole was plugged twelve times with this mix over a period ofabout 52 hours. In each case the tap hole was successfully plugged, andthe mix hardened satisfactorily. When the hole was drilled out to tapthe furnace it was apparent that the plug formed with the tap hole mixof the invention was more refractory than a conventional plug formedfrom a clay-water mix, for the drilled hole was not enlarged by erosioncaused by the flow of molten iron.

Since the tap hole mix of the invention is substantially free of water,its use has no detrimental effect on the carbon lining of the furnace inthe vicinity of the tap hole. Further, it has the property of depositingcarbon when the volatile materials of the binder are decomposed by theheat of the furnace, and thus tends to build up a deposit of carbonadjacent the tap hole.

What is claimed is:

1. A substantially water-free, extrudable, thermosetting tap hole mixfor blast furnaces and the like consisting of at least one comminutedsolid selected from the group consisting of clay, fire brick, coal andcoke and a binder comprising tar and furfural, in a proportion by Weightof about 2 parts tar to 1 part furfural said solid being present in aproportion about 3 to 5 times by weight the proportion of binder.

2. A substantially water-free, extrudable, thermosetting tap hole mixfor blast furnaces and the like consisting of comminuted clay and abinder comprising tar and furfural, in a proportion by weight of about 2parts tar to 1 part furfural said clay being present in a' proportionabout 3 to 5 times by weight the proportion of binder.

3. An extrudable, thermosetting tap hole mix for blast furnaces and thelike consisting by Weight of 80% to 82% of at least one cornminutedsolid selected from the group consisting of clay, fire brick, coal andcoke; 11% to 12% tar; 5% to 6% furfural and 1% to 2% sulfur.

4. A substantially Water-free extrudable thermosetting tap 'hole mix forblast furnaces and the like consisting of a comminuted solid refractoryfiller and I; a binder of an anhydrous heat hardenable phenol aldehydereaction product, said binder being present in a proportion about /3 to/5 by Weight of said comminuted filler.

5. A substantially Water-free extrudable thermosetting tap hole mix forblast furnaces and the like, consisting of a comminuted ceramic filler,a cornminuted carbonaceous filler and a binder, comprising tar andfurfural, in a proportion by weight of about 2 parts to 1. part offurfural, said fillers being present in a proportion of about 3 to 5times by Weight the proportion of binder.

References Cited in the file of this patent UNITED STATES PATENTS357,105 Snyder Feb. 1, 1887 2,122,960 Schwartzwalder July 5, 19382,407,868 Burke Sept. 17, 1946 FOREIGN PATENTS 1,569 Great Britain 1887

1. A SUBSTANTIALLY WATER-FREE, EXTRUDABLE, THERMOSETTING TAP HOLE MIXFOR BLAST FURNACES AND THE LIKE CONSISTING OF AT LEAST ONE COMMINUTEDSOLID SELECTED FROM THE GROUP CONSISTING OF CLAY, FIRE BRICK, COAL ANDCOKE AND A BINDER COMPRISING TAR AND FURFURAL, IN A PROPORTION BY WEIGHTOF ABOUT 2 PARTS TAR TO 1 PART FURFURAL SAID SOLID BEING PRESENT IN APROPORTION ABOUT 3 TO 5 TIMES BY WEIGHT THE PROPORTION OF BINDER.